Mechanical adhesion of copper metallization to dielectric with partially cured epoxy fillers

ABSTRACT

In some embodiments, an improved mechanical adhesion of copper metallization to dielectric with partially cured epoxy fillers is presented. In this regard, a substrate build-up film is introduced having epoxy material and a plurality of epoxy microspheres, wherein an interior of the microspheres is not fully cured. Other embodiments are also disclosed and claimed.

PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/867,851, filed Apr. 22, 2013, which is a divisional of U.S.application Ser. No. 12/059,031, filed Mar. 31, 2008, now issued as U.S.Pat. No. 8,425,785, each of which is incorporated herein by reference inits entirety.

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to the field ofintegrated circuit packages, and, more particularly to improvedmechanical adhesion of copper metallization to dielectric with partiallycured epoxy fillers.

BACKGROUND OF THE INVENTION

The demand for enhanced performance and functionality of integratedcircuit components continues to increase design and fabricationcomplexity. The substrates designed for these components will need to bemanufactured with multiple layers of copper on dielectric material. Thewidth of copper traces is continually shrinking making adhesion ofcopper to dielectric more difficult. One method commonly used to promoteadhesion of copper to dielectric build-up material is desmear. Desmeartypically involves treating an organic substrate surface with a swellerto infiltrate polymer free volume and prepare the surface for oxidation,an oxidizing agent such as permanganate or chromate to promote microroughness by oxidizing polar species on the surface and near the surfaceof the dielectric, and a neutralizer to remove any reaction by-productsor solvents from the previous steps and de-swell the matrix. However,higher average roughness alone will not necessarily result in betteradhesion or higher peel strength. Adhesion is strongly dependent on thesurface profile formed on the surface after desmear.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements, and in which:

FIG. 1 is a graphical illustration of a cross-sectional view of abuild-up film, in accordance with one example embodiment of theinvention;

FIG. 2 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention;

FIG. 3 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention;

FIG. 4 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention; and

FIG. 5 is a block diagram of an example electronic appliance suitablefor implementing an IC package substrate with conductor structure ondielectric material, in accordance with one example embodiment of theinvention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the invention. It will be apparent, however, to oneskilled in the art that embodiments of the invention can be practicedwithout these specific details. In other instances, structures anddevices are shown in block diagram form in order to avoid obscuring theinvention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

FIG. 1 is a graphical illustration of a cross-sectional view of abuild-up film, in accordance with one example embodiment of theinvention. In accordance with the illustrated example embodiment,build-up film 100 includes one or more of dielectric material 102, epoxymicrospheres 104 and filler 106.

Dielectric material 102 represents an organic dielectric material, suchas epoxy based dielectric. In one embodiment, dielectric material 102 isat least partially cured. In another embodiment, dielectric material 102is uncured until being laminated onto a package substrate. As such,while shown as having a shape in FIG. 1, build-up film 100 may be fluiduntil further processing steps.

Epoxy microspheres 104 represent partially cured epoxy filler sphereswherein an interior of the microspheres in not fully cured. In oneembodiment, epoxy microspheres 104 are formed by jetting uncured epoxyinto a jetting tower that partially cures the exterior of the epoxymicrospheres 104 while leaving the interior of epoxy microspheres 104uncured. In another embodiment, the interior of epoxy microspheres 104is partially cured. The exterior of epoxy microspheres 104 may bepartially or fully cured. In one embodiment, epoxy microspheres 104 havea diameter of from about 1 to about 2 micrometers. In one embodiment,epoxy microspheres 104 have a concentration within build-up film 100 offrom about 3 to about 5 volume percent.

Filler 106 may represent silica spheres, such as SiO₂, which maydecrease the coefficient of thermal expansion of build-up film 100.

FIG. 2 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention. As shown, package substrate 200 includesone or more of build-up film 100 coupled with metallization layer 202.

Metallization layer 202 may represent a substrate's metal layer on acore epoxy material or a plated conductive layer. In one embodiment,build-up film 100 is laminated on metallization layer 202 after adhesionpromoter treatment of the Cu, and then cured. In another embodiment,build-up film 100 is not fully cured until after further processing. Theexterior of epoxy microspheres 104 is substantially non-thermallyconductive and should minimize further curing of the interior of epoxymicrospheres 104.

FIG. 3 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention. As shown, package substrate 300 includesone or more of build-up film 100, metallization layer 202, build-up filmsurface 302, via opening 304 and microsphere cavities 306.

Via opening 304 may be formed in build-up film 100 by laser drillingfrom build-up film surface 302 to expose portions of metallization layer202. Via openings may also be formed by punching or mechanical drilling.Next, desmear is performed on build-up film surface 302 and the walls ofvia opening 304 to promote roughness and remove any smear residue fromthe via opening process. On areas in build-up film 100 which consist ofdielectric material 102, a regular roughness profile would emerge.However, due to the presence of epoxy microspheres 104, their subjectionto swelling and microetch in desmear will provide a faster etch rate atthese specific locations as compared to dielectric material 102 due tothe fact that they have undergone less curing than the bulk of the film.In one embodiment, the microetch, for example potassium permanganate,will preferentially attack and remove the interiors of exposed epoxymicrospheres 104, creating microsphere cavities 306. In one embodiment,from about 3 to about 4 micrometers of build-up film 100 is etched off.One skilled in the art would appreciate that the topology of the surfacecan be tuned and well controlled to create the roughness profiledesired, for example with low average roughness (Ra) but high roughnessdepth (Rz), due to pores which extend into the matrix based on the sizeand concentration of the epoxy microspheres 104.

FIG. 4 is a graphical illustration of a cross-sectional view of apartially formed IC package substrate, in accordance with one exampleembodiment of the invention. As shown, package substrate 400 (onlypartially shown here) includes one or more of build-up film 100,metallization layer 202, via opening 304, microsphere cavities 306, andcopper plating layer 402.

Copper plating layer 402 represents copper that has adhered to build-upfilm 100 (and exposed metallization layer 202), plating via opening 304and filling microsphere cavities 306 through electro-less andelectrolytic plating [note that standard electroless plating thicknessis ≦0.8 um, hence may not be able to fill a 2 um void formed by epoxymicrosphere etch]. In one embodiment, electroless copper plating layer402 forms a seed layer for a subsequent metallization layer, which canbe deposited by electrolytic Cu plating. One skilled in the art wouldrecognize that copper plating in microsphere cavities 306 creates deepanchors that should yield improved mechanical adhesion between copperplating layer 402 and build-up film 100 and therefore higher peelstrength.

In one embodiment, package substrate 400 is coupled with an integratedcircuit die such as a flip chip silicon die to form an integratedcircuit package. In another embodiment, additional build-up and/ormetallization layers are formed on package substrate 400 as part of acontinued build-up process.

FIG. 5 is a block diagram of an example electronic appliance suitablefor implementing an IC package substrate with improved mechanicaladhesion of copper metallization to dielectric, in accordance with oneexample embodiment of the invention. Electronic appliance 500 isintended to represent any of a wide variety of traditional andnon-traditional electronic appliances, laptops, desktops, cell phones,wireless communication subscriber units, wireless communicationtelephony infrastructure elements, personal digital assistants, set-topboxes, or any electric appliance that would benefit from the teachingsof the present invention. In accordance with the illustrated exampleembodiment, electronic appliance 500 may include one or more ofprocessor(s) 502, memory controller 504, system memory 506, input/outputcontroller 508, network controller 510, and input/output device(s) 512coupled as shown in FIG. 5. Processor(s) 502, or other integratedcircuit components of electronic appliance 500, may be housed in apackage including a substrate described previously as an embodiment ofthe present invention.

Processor(s) 502 may represent any of a wide variety of control logicincluding, but not limited to one or more of a microprocessor, aprogrammable logic device (PLD), programmable logic array (PLA),application specific integrated circuit (ASIC), a microcontroller, andthe like, although the present invention is not limited in this respect.In one embodiment, processors(s) 502 are Intel® compatible processors.Processor(s) 502 may have an instruction set containing a plurality ofmachine level instructions that may be invoked, for example by anapplication or operating system.

Memory controller 504 may represent any type of chipset or control logicthat interfaces system memory 508 with the other components ofelectronic appliance 500. In one embodiment, the connection betweenprocessor(s) 502 and memory controller 504 may be referred to as afront-side bus. In another embodiment, memory controller 504 may becoupled with processor(s) 502 through a point-to-point serial interface.

System memory 506 may represent any type of memory device(s) used tostore data and instructions that may have been or will be used byprocessor(s) 502. Typically, though the invention is not limited in thisrespect, system memory 506 will consist of dynamic random access memory(DRAM). In one embodiment, system memory 506 may consist of Rambus DRAM(RDRAM). In another embodiment, system memory 506 may consist of doubledata rate synchronous DRAM (DDRSDRAM).

Input/output (I/O) controller 508 may represent any type of chipset orcontrol logic that interfaces I/O device(s) 512 with the othercomponents of electronic appliance 500. In one embodiment, I/Ocontroller 508 may be referred to as a south bridge. In anotherembodiment, I/O controller 508 may comply with the Peripheral ComponentInterconnect (PCI) Express™ Base Specification, Revision 1.0a, PCISpecial Interest Group, released Apr. 15, 2003.

Network controller 510 may represent any type of device that allowselectronic appliance 500 to communicate with other electronic appliancesor devices. In one embodiment, network controller 510 may comply with aThe Institute of Electrical and Electronics Engineers, Inc. (IEEE)802.11b standard (approved Sep. 16, 1999, supplement to ANSI/IEEEStandard 802.11, 1999 Edition). In another embodiment, networkcontroller 510 may be an Ethernet network interface card.

Input/output (I/O) device(s) 512 may represent any type of device,peripheral or component that provides input to or processes output fromelectronic appliance 500.

In the description above, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout some of these specific details. In other instances, well-knownstructures and devices are shown in block diagram form.

Many of the methods are described in their most basic form butoperations can be added to or deleted from any of the methods andinformation can be added or subtracted from any of the describedmessages without departing from the basic scope of the presentinvention. Any number of variations of the inventive concept isanticipated within the scope and spirit of the present invention. Inthis regard, the particular illustrated example embodiments are notprovided to limit the invention but merely to illustrate it. Thus, thescope of the present invention is not to be determined by the specificexamples provided above but only by the plain language of the followingclaims.

What is claimed is:
 1. An apparatus comprising: a substrate build-upfilm, wherein the build-up film comprises: an epoxy material; and aplurality of epoxy microspheres, wherein an interior of the microspheresis not fully cured and an exterior formed from the same material as theinterior, is more cured than the interior.